And after seen all this you still think it's miner related ? 
Absolutely... you've missed this:
At the same time xmr-stak or xmrig works fine
Something strange exactly in bunch srbminer with electroneum.hashvault or electroneum.miningpoolhub. With etn.nanopool works fine.
I've had the same thing happen a few times over the last few weeks. Prefer SRBMiner so switched to Nanopool and no more issues. And Nanopool just reduced their fixed diff from 240000 to 120000 so now getting more shares on lower hash rigs and and more consistent shares. Weird.